1. Field of the Invention
The present invention relates to a method of manufacturing a silicon device having a thin-film pattern on a silicon substrate. Particularly, the present invention is preferably applied to a liquid jet head and a manufacturing method thereof. Specifically, in the liquid jet head, a part of a pressure-generating chamber which communicates with a nozzle orifice ejecting an ink droplet is formed of a vibration plate, a piezoelectric element is formed on a surface of this vibration plate and the ink droplet is ejected by displacement of a piezoelectric layer.
2. Description of the Related Art
As a liquid jet apparatus, there is, for example, an ink-jet recording apparatus including an ink-jet recording head having: a plurality of pressure-generating chambers which generate pressures for ejecting ink droplets by use of a piezoelectric element or a heater element; a common reservoir which supplies ink to each of the pressure-generating chambers; and nozzle orifices which communicate with the respective pressure-generating chambers. In this ink-jet recording apparatus, an ejecting energy is applied to the ink in the pressure-generating chambers communicating with nozzles corresponding to a print signal, and thereby ink droplets are ejected from the nozzle orifices.
In the ink-jet recording head, a part of each pressure-generating chamber communicating with the nozzle orifice ejecting an ink droplet is formed by a vibration plate, and this vibration plate is deformed by the piezoelectric element. Thereafter, ink within the pressure-generating chambers is pressurized and thus the ink droplets are ejected from the nozzle orifices. There are two types of ink-jet recording heads which have been put to practical use, which include: one using a piezoelectric actuator of a longitudinal vibration mode, which extends and contracts in an axial direction of a piezoelectric element; and one using a piezoelectric actuator of a flexure vibration mode.
The former can change a volume of the pressure-generating chamber by allowing an end face of the piezoelectric element to abut on the vibration plate and can be manufactured as a bead suitable for high-density printing. On the other hand, a difficult process of cutting the piezoelectric element into a comb-teeth shape by allowing the piezoelectric element to coincide with an array pitch of the nozzle orifices, and work of aligning the cut piezoelectric elements with the pressure-generating chambers and fixing the piezoelectric elements thereto are required. Thus, there arises a problem that a manufacturing process thereof is complicated.
On the contrary, in the latter, the piezoelectric elements can be fabricated in the vibration plate by a relatively simple process of attaching a green sheet, a piezoelectric material, to the vibration plate in accordance with a shape of the pressure-generating chamber and performing baking thereof. Nevertheless, because of the use of flexure vibration, a certain area is required. Thus, there arises a problem that high-density arrangement is difficult.
Meanwhile, in order to resolve the inconvenience of the latter recording head, there is proposed one in which a uniform piezoelectric material layer is formed across the entire surface of the vibration plate by use of a deposition technology, and this piezoelectric material layer is cut into a shape corresponding to pressure-generating chambers by use of a lithography method. Piezoelectric elements are thus formed so as to be independent for each of the pressure-generating chambers [for example, Japanese Patent Laid-Open No. Heisei 5 (1993)-286131 (FIG. 8, Paragraph 0013)].
According to the above-described proposal, work of attaching the piezoelectric elements to the vibration plate is no longer required and the piezoelectric elements can be fabricated with high density by use of an accurate and simple method such as the lithography method, In addition, there is an advantage that a thickness of the piezoelectric element can be reduced and thus high-speed drive becomes possible.
As a method of manufacturing an ink-jet recording head of this kind, a vibration plate and piezoelectric elements are first formed on one side of a silicon wafer that is to be a passage-forming substrate and, thereafter; a sealing plate is joined with the silicon wafer. The sealing plate includes a piezoelectric element holding portion having an area which does not interfere with movement of the piezoelectric elements at the side of the piezoelectric elements on the silicon wafer. Subsequently, after forming pressure-generating chambers by etching the silicon wafer from the other side thereof, the head is formed by dividing the silicon wafer into a plurality of pieces [for example, Japanese Patent Laid-Open No. 2002-036547 (FIGS. 3 and 4, pp. 6 and 7)].
However, in joining the sealing plate with the silicon wafer, the height at which the silicon wafer abuts on the sealing plate becomes uneven depending on the lamination state of the thin-film pattern formed on the silicon wafer. Thus, there occurs a region where an adhesive agent is formed thick in joining them.
Accordingly, there arises a problem that an etching solution such as an alkaline solution used in etching the silicon wafer intrudes into the piezoelectric element holding portion via the adhesive agent, and thus the piezoelectric elements are damaged.
Moreover, there is another proposal of an ink-jet recording head having a structure in which an insulation layer and a wiring connection layer are sequentially laminated on electrodes of piezoelectric elements or on extraction electrodes together with the piezoelectric elements on a silicon wafer, thus preventing a voltage drop of a common electrode of the respective piezoelectric elements. However, with such a structure, there is a problem that the thickness of an adhesive agent in a region where the silicon wafer and a sealing plate are joined becomes thick and, particularly, an etching solution intrudes into a piezoelectric element holding portion via the adhesive agent.
Furthermore, needless to say, such problems as described above similarly exist not only in the method of manufacturing the ink-jet recording head ejecting ink but also in a method of manufacturing a silicon device such as another liquid jet head ejecting a liquid other than ink.